1. Field of the Invention
This invention relates to optical data storage systems. More specifically, this invention relates to an optical reading and recording apparatus and method for optical data storage systems having multiple data storage surfaces.
2. Description of the Prior Art
Initialized by the vast increase in information that needs to be processed, optical data storage system have become most important system particularly because of their high storage density per area. Most of the recent optical information storage systems rotating single optical disk are used on which the information is digitally stored in concentric circular tracks in an ordered, predifined manner to allow chronological fast reading and fast random access to desired pits of data.
In order to accomplish the even more storage capacity of optical disk systems for the enormous information processing, such as video or picture communication like so called video-on-demand service, multiple disk systems have been proposed. An optical disk system having two or more data layers may in theory be accessed at different disks by changing the focal point with moving lens. Example of this type of state-of-the-art include U.S. Pat. No. 5,202,875 issued Apr. 13, 1993 to Rosen, et al.; Japanese published application, 63-276732 published Nov. 15, 1988 by Watanabe, et al.
The serious problem with these prior art systems is an interference lights reflected on neighboring layers, that causes difficulty to detect the data recorded on certain layer. That cross-talk-signals from the other layers may effect critically to reduce the ability to read the data, especially with several data layers system. In addition, all of the prior art systems requires the moving lens component which is very difficult to control and impossible to fabricate on a single substrate. That has been considered disadvantage on productivity and reliability. An optical reading and recording pick-up device is needed which overcomes these problems mentioned above.